The invention relates to a method for operating an internal combustion engine, in particular a diesel engine, an apparatus for carrying out the method, and a vehicle, in particular a utility vehicle, for carrying out the method and/or having the apparatus.
It is known to provide an external exhaust-gas recirculation device on an internal combustion engine, so that exhaust gas emitted by the internal combustion engine can be fed back to the internal combustion engine. In this way, pollutants, in particular nitrogen oxides, contained in the exhaust gas of the internal combustion engine can be reduced.
It is also generally known that, to increase the efficiency of the internal combustion engine and to realize a corresponding lowering of the fuel consumption of the internal combustion engine, the combustion air fed to the internal combustion engine can be compressed by a compressor of an exhaust-gas turbocharger. Here, a particularly effective increase in efficiency can be realized by two-stage supercharging with intercooling. The compression of the combustion air however normally leads to an increase of the peak temperatures in the combustion process, whereby the amount of nitrogen oxides emitted by the internal combustion engine is also increased.
Furthermore, owing to the compression of the combustion air, at high torques or high mean pressures of the internal combustion engine, external exhaust-gas recirculation is impeded owing to the high pressure of the combustion air flowing through the intake tract and a simultaneously increasing positive scavenging gradient. Measures for increasing the recirculation rate reduce the effectiveness of the process recirculation and, owing to the increased fuel consumption, lead to a further increase of the emitted nitrogen oxides. To nevertheless be able to comply with applicable exhaust-gas regulations, it would for example be possible, in the case of an SCR catalytic converter being used, for the amount of an aqueous urea solution (“AdBlue”) introduced into the exhaust tract upstream of the SCR catalytic converter to be increased. This however entails increased operating costs and, if the internal combustion engine is provided in a vehicle, a reduction of the range of the vehicle.